Polymeric materials have one important deficiency which must be overcome before they can be used in various commercial applications. This deficiency is the susceptibility to oxidative and actinic degradation. Many varieties of compounds have been known to be useful as stabilizers of various polymers, but all of them have certain deficiencies which limits the usefulness of such stabilizers. Thus, one class of stabilizers disclosed in the prior art that is related to the compounds of this invention is hindered hydroxybenzoates disclosed in U.S. Pat. Nos. 3,029,276; 3,112,338; 3,206,431 and 3,502,613.
Most of the compounds disclosed in said patents are various esters of 3,5-dialkyl-4-hydroxybenzoic acids while this invention deals with 4-(3,5-dialkyl-4-hydroxybenzoyloxy)-mono or dialkylbenzamides. Other differences are that the phenyl ring in the benzoate ring is completely unsubstituted while the corresponding group in the compounds of this invention has at least one alkyl substituent.
The compounds of this invention have many advantages over the prior art compounds. The instant compounds have improved thermal stability. This feature is important because the polymer substrates are subjected to high temperature processing during manufacturing stages. Furthermore, the compounds of this invention have better gas fading properties and have better aqueous and organic solvent extraction resistance than the prior art compounds.